In a liquid crystal display device (display device) on which a non-emission type liquid crystal display panel (display panel) is mounted, usually a backlight unit (lighting system) which supplies light to the liquid crystal display panel is also mounted thereon. It is preferable that the backlight unit is configured so as to generate sheet-shaped light which diffuses all over a planar liquid crystal display panel. For this reason, there is a case in which the backlight unit which is mounted on the liquid crystal display panel includes a light guiding plate (light guiding member) for effectively mixing light from a light source which is built therein.
As a backlight unit which includes a light guiding plate, for example, an edge light-type (side light-type) backlight unit has been known. In general, the edge light-type backlight unit has a configuration in which a light source such as a Light Emitting Diode (LED), or the like, is arranged on the side surface of a light guiding plate. In the backlight unit having such a configuration, light which is emitted from a light source is input to the inside of the light guiding plate from the side surface of the light guiding plate, and the input light is emitted to the liquid crystal display panel side by being guided in the light guiding plate.
Here, when a point light source such as an LED is used as a light source in the edge light-type backlight unit, it is difficult to make light uniformly input to a wide light guiding plate. For this reason, in a backlight unit in which the LED is used as the light source, uneven luminance easily occurs.
For this reason, in the related art, a lighting system which is capable of obtaining uniform emission light even when a point light source such as an LED is used has been proposed (for example, refer to PTL 1).
In PTL 1, a lighting system in which a trapezoidal shape is protruded at a position corresponding to a point light source in a light guiding plate, and through holes of a triangular shape or a trapezoidal shape which is symmetric are provided in the trapezoidal shape is disclosed. In the lighting system, light which is input to the light guiding plate is horizontally diffused by reflecting the light from a light source on the protruded trapezoidal side surface, or on the side surface of the through hole. In this manner, it is possible to obtain more uniform emission light.